Refining of mineral oils



Patented Mar. 26, 1946 REFINING F MINERAL OILS James C. .Alspaugh,Baytown, Tex., assignor to Standard Oil Development Company, acorporation of Delaware Application December 7, 1940; Serial No.369,036-

Claims.

The present invention relates to the refinin of mineral oils. Theinvention is more particularly concerned. with the refining of petroleumoils boiling in the motor fuel, kerosene, and gas oil boiling ranges andespecially relates to an improved process for the removal ofobjectionable compounds therefrom when utilizing as a treating agent, amineral acid such as a sulfuric or an equivalent acid. In accordancewith the present process, acid treated oils after removal of the acidsludge are subjected in an initial stage to a washing operation in whichthe solvent comprises an aqueous solution of calcium chloride andsubsequently contacted in a secondary stage with a neutralizing agent.

It is well. known in the art to refine mineral oil's, particularlypetroleum oils, by Various procedures involving distillation, acidtreating, clay treating and neutralization stages. For example, it isknown in the art to remove objectionable sulfur and related compoundsfrom petroleum oils, particularly from those oils boiling in the motorfuel boiling range, by treating the same. with suitable mineral acids.After a suitable contacting period, the spent acid sludge solutioniisremoved from the oil which is subsequently treated with a suitablesolvent which usually comprises water in order to remove free acidicconstituents. The oil, after removal of the washing solvent, iscompletely neutralized by treating the same with an alkali treatingagent such as an aqueous solution of sodium hydroxide. In theseoperations the mineral acid usually comprises an acid of sulfurparticularly sulfuric acids of various concentrations. The acid.treating operation generally is conducted under conditions tosecure amaximum removal of the objectionable sulfur compounds and a minimumdegradation of the valuable petroleum oil constituents. Usually, theoperations are conducted at temperatures in the range from about 70 F.to 80 F. and at atmospheric pressures, although lower temperatures maybe employed- The mixture after a sufiicient time of contact is handledin a manner to remove the acid sludge which. contains the objectionablesulfur and other undesirable compounds. The oil after separation of theacid sludge is generally termed acid oil. This acid oil contains smallquantities of acid particles as well as small quantities of sludgeparticles. In addition, the oil also containsdissolved sulfuric acidconstituents.

In order to remove these constituents from the oil and to produce afinished product of the desired quality, it has heretofore been thepractice to treat the acid oil in an initial stage with a washingsolvent which usually comprises water. After removal of the water, theoil is completely neutralized in a neutralization stage by treating thesame with an. alkali. metal hydroxide solution; generally with. a sodiumhydroxide solution.

In these processes, particularly in operations involving the continuousacid treating, water washing and caustic neutralizati'onyofpetroleumoils boiling in the motor fuel. boiling range, variousdifficulties are incurred. For example. if the acid oiI be treated witha relatively light water wash in which. approximately 2% to 5 of waterbased on the oil is utilized, satisfactory removal of the acidicconstituents is not obtained. This results in a material increase in theamount of caustic required in order to completely neutralize the oil. Onthe other hand, if a relatively large. quantity of water be used, as forexample a 10 or higher water wash based on the oil, a more satisfactoryremoval of the acid constituents is obtained, but in many cases.particularly when treating cracked naphthas. deleterious emulsionsresult which are difficult to break. These: emulsions causeanappreciable loss of the oil in the water which is passed to the sewer.Furthermore, acid water is also removed with the oil stream which issubsequently neutralized.

I have, however, now discovered a process by which improved results aresecured in an operation for the removal of sulfur compounds from feedoils when utilizing a mineralacid such as a sulfuric acid. In accordancewith my process,

the acid oil after removalof the-acid sludge, is

contacted with an aqueous solution containing dissolved therein a. smallamount of calcium chloride. Aftera sufiicient contacting period, the

calcium chloride treated oil, is removed from the calcium chloridesolution and treated with a neutralizing agent which preferablycomprises a sodium hydroxide solution.

My invention may be readily understood by reference to the attacheddrawing illustrating amodificati'oll of the same. For purposes ofdescription it is assumed that the feed oil comprises a cracked naphthaboiling in the motor fuel boiling range. The feed oil is introduced intothe system by means of line I and is mixed with sulfuric acid which isintroduced by means of line 2. The oil and the sulfuric acid are passedthrough a mixer 3 and introduced into acid settling drum '5 by means ofline 4. The acid sludge settles in zone 5 and is withdrawn from the sameby means of line 6. The acid treated oil is withdrawn from zone 5 bymeans of line I and mixed with water which is introduced into the systemby means of line 8 to which calcium chloride has been added by means ofline 9. The mixture is passed to settling zone I0 in which the aqueoussolution segregates and 'is'withdrawnby means of line H. The calciumchloride treated oil is withdrawn by means of line l2 and mixed with V asodium hydroxide solution which is introduced into the system by meansof line [3. The oil and the sodium hydroxide solution are passed throughmixer l4 and introduced into settling zone, l5 in which'the spentcaustic solution segregates and is withdrawn from'the system by means ofline It. The treated oil is withdrawn from zone l5 by means of line I!and further refined or handled in any manner desirable.

The process of the present invention InayJbe widely varied. Theinvention may be adapted to the treatment of any feed oil but isparticularly the water washing stage is substantially clear and free ofexcessive moisture. In addition, the water stream to the sewer iscompletelyfree of oil which prevents a loss in yields. 1 Materialoperating benefits are also secured since it is pose sible to readilyhold a constant level in the wash 1 drum.

effective in the treatment of petroleum oils'boil ing in the motor fuelboiling range especially in the treatment of cracked naphthas boiling inthis range. The invention essentially comprises treating these feed oilswith'a sulfuric acid in an initial stage, contacting the same with anaqueous calcium chloride solution in a secondary stage,

7 followed by neutralizing-the treated oil with a caustic solution in atertiary stage.

The calcium chloride solution may vary considerably and will depend'uponthe character of the oil and the amount of acid employed in the initialstage. In general, the calcium chloride solution should have a specificgravity in the range from about 1.16 to 1.26.; When employing solutionsof this gravity the concentration of the calcium chloride in the wateris approximately .00135 pound of calcium chloride per gallon of water.However, the amount of calcium chloride may vary in the-range from about.0001 to .01 pound of calcium chloride per gallon of water. A preferredsolutionof water contains from .0010

to .0015 pound of calcium chloride per gallon of water. 7 V 1 The amountof sodium hydroxide solution used per gallon of acid oil being treatedlikewise will depend upon the character of the oil and the concentrationof the calcium chloride. However,

in general, itis preferred to contact the acid oil with from about'5% to30% of sodium hydroxide of 10 B. or equivalent, preferably with about.

% based on the on- In order further to illustrate the invention'thefollowing example is given which shouldnot be construed as limiting thesame in any manner results of these operations were asfollows:

a a Percent of Acidity of Average of operations washed gig gggz lacidoil. ,tosewer Conventional process 0.068 0. 190 Process of presentinvention .023 v 0 (Figi res based on sodium hydroxide equivalent;pounds per barrel Ol V Prom the above it Via-apparent that whenemploying my invention undesirable emulsions-are eliminated. Furthermorethe acidity .ofthe washed oil is reduced in excess of 50% andthe'. oilstream entering the alkali incorporator from r The process of thepresent invention is not to be limited by any theory or mode 'ofoperation but only in and by the following claims in which it is desiredto claim all novelty;

'I claimi f y 1'. Process for the removal of sulfur compounds fromoilscontaining the same which comprises contacting a feed oil in aninitial stage, utilizing a mineral acid, separating the acid sludge-fromthe oil, treating the oil with .a .dilute aqueous solution of calciumchloride, separating the :c'alcium chloride solution and-neutralizingtheioil with an alkali'metal hydroxide solution.

2. Process as defined by claim l'in which the concentration of thecalcium chloride ;.in the aqueous solution isin the range from"abouti.0001 to .Olpound of calcium chlorideper'. gallon of water. m 3.Process for'the removal of sulfur compounds from petroleum oilsboilingin the motor fuel boiling range which comprises contacting a feedoil in an initial stage utilizing a mineral acid, separating the acidsludge from the oil, treating the oil with an aqueous solution ofcalciumchlorlde containing about .0001 to 01 1b.,of; calcium .chloride/gal. of water, separating the calcium chloride solution andneutralizing the oil with an alkali metal hydroxide solution. 1 Y Y 4.Process as defined by claim 3 in'which the mineral acid comprisessulfuric acid. V a

5. Process as definedby claim 3 in which the feed oil comprisesa'cracked petroleum oil, in which the mineral acid comprises sulfuricacid, and in which the alkali metal hydroxide com prises sodiumhydroxide.

a; Process for'the removai of "objectionable compounds. from crackedpetroleum-oils which comprises contacting the same in an "initial'stageutilizing a mineral acid, separating the acid sludge from the oil,treating the oil with a dilute aqueous solution of calcium chloride,separating the calcium chloride solution and neutralizing the; oil withan'alkali metal hydroxide solutions '7.Process as defined by claim Ginwhichi-the mineral acid comprises sulfuric acid.

8. Process as defined by claim 6 in which the.

mineral acidcomprises sulfuricfacid and in which the concentration'ofthe calcium chloride in the 7 aqueous solution is in the range fromabout .0001

to .01 pound of water.

'9. The process of refining mineral oils which comprisestreating apetroleum oil distillate selected from the'g'roup consisting of naphtha,kerosena'and' gas oil boiling range with sulfuric acid at a temperaturenot above-about F., separating the major proportion of the resultantacid sludgefrom the oil, treating the residual acid oil, which stillcontains snjiall 'quantitiesf'ofla' material selected from the groupconsistingfjof acid and sludgejwith water'containing a small amount ofcalcium chloride dissolved therein in just sumcient amount to "assistsubstantiallyin theremoval of. acid and sludgeparticles retained in theacid oil and to prevent'emulsion formation, separating the calciumchloride solution from'the oil, andfinally neutralizing any remainingtraces calcium I chloride "per gallon of 1 of acid in the oil by washingwith an alkali metal hydroxide solution.

10. The process which comprises treating cracked naphtha with sulfuricacid at a temperature not above 80 F., settling and removing theresultant acid sludge from the naphtha, treating the naphtha with watercontaining about .0001

to .01 lb. of calcium chloride/gal. of water, separating the calciumchloride solution from the naphtha, and subjecting the latter to anacidneutralizing treatment with about 5-30% of an aqueous solution ofsodium hydroxide of about 10 B. concentration.

JAMES C. ALSPAUGI-I.

